Long piston rods and motor embodying the same



April 19, 19 w. cs. BALDENHOFER 2,932,985

LONG PISTON RODS AND MOTOR EMBODYING THE SAME Original Filed Feb. 8,1954 NW o IN V EN TOR.

'wuunn c. BHLDENHOFER United States Patent LONG PISTON RODS AND MOTOREMBODYING THE SAME William G. Baldenhofer, Springfield, Ohio, assignorto The Thompson Grinder Company, Springfield, Ohio, a corporation ofOhio Original application February 8, 1954, Serial No. 408,903. Dividedand this application March 19, 1956, Serial No. 572,301

1 Claim. (Cl. 74-579) This invention relates to piston rods and likeelongated members, particularly to extremely long piston rods and tomotors having such rods, and the like, and is a division of myco-pending application, Serial No. 408,903, filed February 8, 1954, andnow abandoned.

Many times it becomes necessary to employ an elongated rod as a tensionor compression member in the manufacture of machine tools and similardevices, and inparticular a machine tool having an extremely long tabletravel, where the table is driven by a hydraulic motor and an extremelylong element must be employed in the form of a piston rod for connectingthe table with the piston, by means of which it is actuated.

In the case of machine tools having extremely long table travels, it hasbeen customary to drive the table by means of a rack and pinion becauseof the difiiculty encountered in connection with the extremely longpistion rods that would be required to replace the rack and pinion. Thehydraulic actuation of a table is preferred because, with a rack andpinion, the speed of movement of the table will vary slightly as eachtooth of the pinion meshes with the rack. In some instances this slightvariation in speed is not important, but wherever a very finely finishedsurface is to be produced on the machine as, for example, when afinished grind is being taken on a surface these slight variations inspeed will result in marks occurring on the surface being finished.

Heretofore, when machine tool tables were driven over long distances byhydraulic motors, the sagging of the piston rod between the ends thereofinduced objectionable wear on the packing or the rod, or both thereof,and the rod would tend to whip when the direction of travel of the tablewas reversed.

The development of a packless cylinder minimized the objectionablefeature of wearing of the piston packing when the rod was passedtherethrough, but the objection still existed in that the rod would tendto whip and likewise the piston on the rod would tend to slightly cockin the cylinder, thus promoting objectionable wear on the cylinder andthe piston packing.

Having the foregoing in mind, it is a particular object of the presentinvention to provide a piston rod which overcomes the drawbacks referredto above so that, by use of a rod according to this invention, a machinetool table can be driven over as long a distance of travel as isnecessary without rod sag becoming objectionable.

A still further object of the present invention is the provision of ahydraulic motor assembly for driving the table for a machine tool or thelike, in which there is no objectionable sagging of the piston rod inany position thereof in the hydraulic cylinder of the motor.

Another particular object of this invention is the provision of ahydraulic motor arrangement for driving a machine tool table or thelike, in which the objectionable features of whipping or yielding of thepiston rod of the hydraulic motor is eliminated.

These and other objects and advantages of this invention will becomemore apparent upon reference to the 2,932,985 Patented Apr. 19,1960

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2 following specification taken in connection with the accompanyingdrawings, in which:

Figure 1 is a view of a grinding machine having a long bed, and with thebed in section to show the hydraulic motors which actuate the table;

Figure 2 is a sectional view showing the internal construction of one ofthe motors of Figure l and is indicated by line 2-2 on Figure 1;

Figure 3 is a more or less diagrammatic view showing the piston rodbeing treated according'to this invention; and

Figure 4 is a fragmentary view showing a key way being cut in the rodafter its treatment in order to orient the rod with the bracket whichconnects it with the table in the machine.

Referring to the drawings somewhat more in detail,

the machine illustrated in Figure 1 comprises a bed 10 I wheel head unit18 having a motor-driven grinding wheel 20 adapted for being broughtinto grinding relation with work on table 12.

For driving table 12, there is provided. a bracket 22 at one end whichis connected with a piston rod 24 that extends substantially the lengthof the table :and terminates in a piston 26 reciprocable in cylinder 28that is adapted for being supplied with pressure fluid via conduit 30.

Table 12 has a similar bracket 32 at its opposite end connected topiston rod 34 having piston 36 located in the cylinder 3% in the bed,and which cylinder is provided with conduit 49 for supplying pressurefluid thereto.

in Figure 2 it will be seen that the cylinders of the hydraulicmotors-the lefthand motor being illustrated in Figure 2are withoutpacking and that, instead, the piston 36 on the end of the piston rod 34consists of the packing material 41 compressed between the ring 42 onthe piston rod and the gland nuts 44 threaded on the extreme end of therod.

It will also be seen in Figure 2 that the piston rods are hollow, thustaking the form of tubes, and that at the bracket end of the rod it isprovided with a closure member 46 threaded at 48 into the end of the rodand welded thereto as at 50. The closure member 46 comprises a part 52keyed to bracket 22 by key 54 and clamped thereto by nut 56.

The left end of cylinder 38 is threaded into support lock 53, to whichconduit 40 is connected and carried by the support block, and clampedthereto by cylinder 3 is a member 6h having the radially open ports 62and the axial passage 6 Check valve 66 closes passage 6% against flowtherethrough in the leftward direction while permitting flowtherethrough in the rightward direction.

Member 69 tapers inwardly somewhat toward the right and, at its left endin the region of ports 62, is a fairly close fit within rod 34.

The described arrangement provides for free flow of actuating fluidrightwardly through passage 64 into the interior of rod 34, whereby thepressure will drive the rod and the connected parts rightwardly;whereas, when the rod is driven leftwardly by movement of the table 12in the opposite direction, the fluid that is expelled from the interiorof the rod must pass through the ports 62, and when flow to these portscommences to be restricted by the member 60 entering the left end of rod34 a damping and shock-absorbing effect is had on table 12 that ends bytreating it according to the diagrammatic illustration in Figure. 3.

In Figure 3 the. rod is indicated at 70 and is sup ported on the spacedbrackets 72 and 74 located apart approximately the same distance thatthe points of support of the rod will be when fully extended in use. In

Figure 3, the actual sag of the rod has been considerably exaggerated;but it will be appreciated that for a rodof,

say 2 5 feet in length, the sag could approach one-fourth ofan' inch atthe center.

According to the present invention the rod is drawn up-for asubstantially horizontal position by applying heat to the top fibersthereof by means of a small torch as'at 76, which advantageously is anacetylene torch, which preferably is-adjusted so as to have anon-oxidizing flame. This torch is-moved lengthwise of the rod, and

theapplication of localiied heat to the compressed fibers along the topof'the rod will cause expansion thereof so that the rod is brought up towhere it extends substantially straight between the supports 72 and '74.The degreeofheat so applied will vary and, while no accurate measurementhas been made of the temperature that the rod reaches during thistreatment, it has been noted that the rod does not reach red heat andthat, even with a polished rod, the polish does not discolor after thestressing treatment according to this invention.

Preferably, the torch 76 is followed by a quenching head 78 whichsupplies a small stream of cooling water to the rod to bring it back toroom temperature. This chilling of the rod, after heating thereof,apparently sets the fibers of the rod so that it remains in horizontalposition after the heat has been removed therefrom.

It'will be apparent that inasmuch as piston rods of this nature willvary considerably as to their, stroke, some being tubular as illustratedin this application, they will vary considerably in diameter and, as tothe degree of sag that must be counteracted and the exact tempermine atwhich the rod will be raised and the length of time it must bemaintained atthat temperature, will vary somewhat and thus no specificlimits are intended to be implied by stating that the rod referred towas not elevated to red heat and that the torch is moving relativelyslowly therealong.

In Figure 3 the apparatus for treating the rod is illustrateddiagrammatically with screw 73 supporting block 75 that carries torch 76and quenching head 78. Motor 77 drives the screwito move the block alongthe rod at a predetermined rate. valved-conduit 79 supplies a coolingmedium to quenching head 78 while valved conduits 31 and S3 supply fueland an oxidizertheree' for in the proper proportion to torch 76.

it will be appreciated that all of these features will vary with alltheparticular results which it is desired to accomplish. j

Following the treatment as described above, it becomes important tolocate the rod in the machine so that the stressed side is upwardly, andwith this in mind I cut a key way 8th in the rod by cutter 82 which isoriented relative to the stressed side of the rod so that when the rodis keyed to the attached bracket therefor the stressed side of the rodWill be located at the proper position. I

it-will be understood that this invention issusc'eptible to:modification in order to adapt it to different usages and conditionsand, accordingly, it is desired to comprehend such modifications withinthis invention as may fall withinthe scope of the appended claim.

I claim:

In a piston and cylinder mechanism, an elongated piston rod having alength and weight which normally would produce an objectionable downwardweight deflection when supported at its ends in a substantiallyhorizontal position, said elongated piston rod having the uppermost ilongitudinally extended surface portion pre-stressed permanently by theapplication of a high temperature flame followed by quenching beingpre-stressed only longitudinally along said uppermost surface of the rodto cause said rod to be bowed upwardly, and wherein the rod will besubstantially straight without sagging when the same is supported at itsopposite endsand the prestressed portion of the rod is positioneduppermost.

References Cited in the file of this patent UNITED STATES PATENTS Dugle-Apr. 3, 1956 l l a l

